Benzopyran derivatives having various pharmacological activities have hitherto been known. For example, various benzopyran derivatives in which the carbon atom at the 4-position of the benzopyran ring is directly bonded to a nitrogen atom are disclosed in Japanese Patent Application Laid-Open Nos. 60-97974, 61-47416, 63-165317, 63-196581, 63-201182, 63-303977, 64-26578, 64-38087, and 2-129184, and Journal of Medical Chemistry, Vol. 33, No. 6, pp. 1529-1541 (1990). The literatures report that these compounds possess antihypertensive activity and are useful for the treatment of heart diseases.
Of the benzopyran derivatives disclosed, Cromakalim having formula: ##STR2## has recently attracted attention as a new type of hypotensires which acts on the K.sup.+ channel, similar to Nicorandil and Pinacidil.
Benzopyran derivatives in which the 4-carbon atom on the benzopyran ring is not bonded directly to a nitrogen atom are disclosed in Japanese Patent Application Laid-Open Nos. 63-303977 and 64-38087, Journal of Heterocyclic Chemistry, Vol. 11, No. 5, pp. 797-802 (1974), and Journal of Medical Chemistry, Vol. 33, No. 6, pp. 1529-1541 (1990).
Further, WO 90/14346 (published on Nov. 29, 1990, after the priority date of the present invention) discloses compounds having an amido group or a thioamido group at the position of the benzopyran ring thereof.